Avrò 683 Lancaster

No one would dispute the statement that the Avrò Lancaster was the finest British heavy bomber of World War II; indeed many would even argue that it was the finest heavy bomber serving on either side during the conflict, and it is therefore strange to recall that it had its genesis in the unsuccessful twinengine Avrò Manchester.

However, it is not entirely true to say that the Lancaster was virtually a fourengine Manchester, as four-engine installations in the basic airframe had been proposed before Manchester deliveries to the RAF began. But the prototype Lancaster was, in fact, a converted Manchester airframe with an enlarged wing outer panels and four 1,145-hp (854-kW) Rolls-Royce Merlin Xs. This prototype initially retained the Manchester's triple tail assembly, but was later modified to the twin fin and rudder assembly which became standard on production Lancasters.

The prototype flew on 9 January 1941 and later that month went to the Aeroplane and Armament Experimental Establishment, Boscombe Down, to begin intensive flying trials.

The new bomber was an immediate success, and large production orders were placed. Such was the speed of development in wartime that the first production Lancaster was flown in October 1941, a number of partially completed Manchester airframes being converted on the line to emerge as Lancaster Mk I (from 1942 redesignated Lancaster B.Mk I) aircraft.

Lancasters soon began to replace Manchesters, and such was the impetus of production that a shortage of Merlin engines was threatened. This was countered by licence-production by Packard in the USA of the Merlin not only for Lancasters but for other types. An additional insurance was effected in another way, the use of 1,735-hp (1294-kW) Bristol Hercules VI or XVI radial engines.

Meanwhile, the Merlin Lancasters were going from strength to strength. The prototype's engines gave way to 1,280-hp (954-kW) Merlin XXs and 22s, or 1,620-hp (1208-kW) Merlin 24s in production aircraft. Early thoughts of fitting a ventral turret were sadly discarded, and the Lancaster B.Mk I had three Frazer-Nash hydraulicallyoperated turrets with eight 7.7-mm (0.303-m) Browning machine-guns: two each in the nose and mid-upper dorsal positions and four in the tail turret, The bomb-bay, designed origmally to carry 1814 kg (4,000 lb) of bombs, was enlarged progressively to carry bigger and bigger bombs: up to 3629 and 5443 kg (8,000 and 12,000 lb) and eventually to Barnes Wallis' enormous 9979-kg (22,000-lb) 'Grand Slam', the heaviest bomb carried by any aircraft in World War II.

The Lancaster's existence was not revealed to the public until 17 August ofthat year, when 12 aircraft from Nos 44 and 97 Squadrons carried out an unescorted daylight raid on Augsburg. Flown at low level, the raid inflicted considerable damage on a factory producing U-boat diesel engines, but the cost was high, seven aircraft being lost, Squadron Leaders Nettleton and Sherwood each received the Victoria Cross, the latter posthumously, for leading the operation, which perhaps confirmed to the Air Staff that unescorted daylight raids by heavy bombers were not a practicable proposition.

It would be true to say that development of the Lancaster went hand-inhard with development of bombs, The early Lancasters carried their bomb loads in normal flush-fitting bomb bays, but as bombs got larger it became necessary, in order to be able to close the bomb doors, to make the bays deeper so that they protruded slightly below the fuselage line. Eventually, with other developments, the bomb doors were omitted altogether for certain specialist types of bomb.

The German battleship Tirpitz was attacked on several occasions by Lancasters until, on 12 November 1944, a combined force from Nos 9 and 617 Squadrons found the battleship in Tromso Fjord, Norway, and sank her with 5443-kg (12,000-lb) Tallboy1 bombs, also designed by Barnes Wallis. The ultimate in conventional high explosive bombs was reached with the 9979-kg (22,000-lb) 'Grand Slam', a weapon designed to destroy concrete by exploding some way beneath the surface, so creating an earthquake effect. No. 617 Squadron first used the 'Grand Slam' operationally against the Bielefeld Viaduct on 14 March 1945, causing considerable destruction amongst its spans.

In spite of the other variants built from time to time, the Lancaster B.Mk I (Lancaster B.Mk 1 from 1945) remained in production throughout the war, and the last was delivered by Armstrong Whitworth on 2 February 1946. Production had encompassed two Mk I prototypes, 3,425 Mk Is, 301 Mk Us, 3,039 Mk Ills, 180 Mk VIIs and 430 Mk Xs, a total of 7,377. These were built by Avrò (3,673), Armstrong Whitworth (1,329), Austin Motors (330), Metropolitan Vickers (1,080), VickersArmstrongs (535) and Victory Aircraft (430). Some conversions between different mark numbers took place.

Statistics show that at least 59 Bomber Command squadrons operated Lancasters, which flew more than 156,000 sorties and dropped, in addition to 608,612 tons (618,350 tonnes) of high explosive bombs, more than 51 million incendiaries.

Armament: 7.7-mm (0.303-in) machineguns (two each in nose and dorsal turrets, and four in tail turret), plus bomb load comprising one 9979-kg (22,000 lb) bomb or up to 6350 kg (14,000-lb) of smaller bombs.

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